Silver-copper-zinc-cadmium alloy



Nov. 8,

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TEMPERATURE (F) R. H. LEACH 2,487,!52

SILVER-COPPER-ZINC-CADMIUM ALLOY Original Filed Aug. 14, 1945 FE G. I

45% ZN PLUS CD |.o/|.0 ZN/GD RATIO WEIGHT PERCENT SILVER F I G. 2 I

45% ZN PLUS CD 3.4/I.O AG/CU RATIO IIOO lllllll IlllllllI lllllll! llll IO 2O 5O 4O WEIGHT PERCENT GADMIUM INVENTOR.

ROBERT H. LEACI-I ATTORNEYS Patented Nov. 8, 1949 SILVER-COPPER-ZINC-CADMIUM ALLOY Robert H. Leach, Fairfield, Conn., assignor to Handy & Harman, New York, N. Y., a corporation of New York Original application August 14, 1945', Serial No. 610,752. Divided and this application January 21, 1949, Serial No. 72,017

2 Claims. (Cl. 75-134) This invention relates to alloys for brazing purposes and is concerned more particularly with novel quaternary alloys of silver, copper, zinc, and cadmium, which possess important advantages over prior similar quaternary brazing alloys. The new alloys flow freely at substantially lower temperatures than the prior alloys and may, accordingly, be employed to greater advantage in brazing heat-treated steels, since, because of the lower temperatures to which they are exposed, such steels sufier less loss of their properties in the brazing operation. Also, the

Y alloys of the invention contain substantially less silverthan the prior alloys, and, as silver is many times more expensive than the other components of such alloys, it will be evident that even a relatively small reduction in the amount of silver used greatly reduces the cost. The new alloys may be readily fabricated into usable iorms by methods in common use and they produce strong joints.

In my Patent No. 2,383,976, which issued on September 4, 1945, I disclosed a quaternary brazing alloy of silver, copper, zinc, and cadmium, containing between 44% and 47.5% silver, and a total amount of zinc and cadmium not exceeding about 40%. In the alloy of that patent, the copper is present in such an amount that the ratio of silver to copper ranges between 2.6 and 3.5, while the ratio of zinc to cadmium varies between 0.9 and 1.2. Alloys of the kind disclosed in the patent have flow points between about 1150 F. and 1160 F.

Further investigation of the properties of quaternary alloys of silver, copper, zinc, and cad-' mium has brought out peculiar features of such alloys that could not have been predicted from prior knowledge, and the present invention is based on the results of such investigation. Prior to the research referred to, it was to be expected from the available knowledge of the properties of the several components of such alloys, that, as the total amount of zinc and cadmium increased, a corresponding decrease in the flow point would ensue. I have discovered, however,

, that the total amount of zinc and cadmium presthe range is exceeded, will produce an increase.

Moreover,

Similarly, an increase in the silver-copper ratio to a critical point will result in a decrease in the flow point of the alloy, but, beyond the critical point, will produce an increase.

The alloys of the present invention are quaternary alloys of silver, copper, zinc and cadmium containing 42.543% silver and 1212.5% copper in a total amount of 551% of the alloy. The remaining 45% of the alloy, composition is composed of the zinc and cadmium in amounts ranging from 15 to 22.5% zinc and 22.5 to 30% cadmium, the ratio of zinc to cadmium ranging from 0.5 to 1.0. These alloys appear to comprise eutectic compositions characterized by a flow point of about 1125 F.

The criticality of the silver and copper contents of the alloys of my invention is illustrated by Fig. 1 of the accompanying drawing. The curve A shown in Fig. 1 represents the flow points of quaternary alloys of silver, copper, zinc and cadmium in which the zinc-cadmium content and ratio are maintained constant at 45% and 1/1, respectively, while the relative amounts of silver and copper are varied although totalling in each instance. Thus, when the silver content is approximately 40.25% and the copper amounts to 14.75%, representing a ratio of about 2.7, the alloy has a flow point of 1150 F. which is about that of the alloys of my patent above identified. If the silver content is increased to 42%, representing a ratio of silver to copper of 3.2, the flow point of the alloy drops to about 1130 F. and the flow point continues to decrease with an increase in the silver, until a silver content of 42.543%, representing a silver-copper ratio of about 3.6, is reached. At this ratio, the lowest flow point of about 1125 F. is obtained. Beyond that critical point in the silver-copper ratio, a further increase in the silver with a consequent increase in the silver-copper ratio results in an increase in the flow point of the alloy, rather than a further decrease. At a silvercopper ratio of 4, the flow point is approximately 1135 F., which is slightly higher than that of the alloy containing silver and copper in a ratio of 3.2.

The criticality of the zinc and cadmium contents of the alloys of my invention is illustrated by the curve B in Fig. 2 of the drawing. The curve represents the flow point of quaternary alloys of silver, copper, zinc and cadmium in which the silver and copper contents, which total 55%, are maintained constant at 42.5% and 12.5%, respectively, while the relative amounts of zinc and cadmium are varied although total- 3 ling 45,% in each instance. It will be noted that these silver and copper contents are virtually those which produced the lowest flow point alloy when a zinc-cadmium ratio of 1/1 was maintained in the balance of the alloy composition. With a cadmium content of 20% and a consequent zinc-cadmium ratio of 1.25, the alloy has a flow point of 1135 F. As the cadmium is increased to about 22.5%, representing a zinccadmium ratio of 1, the flow point falls to 1125 F. A further increase in the cadmium to 30% with a fall in the ratio to 0.5 produces no change in the flow point, but, as the cadmium is increased to 32%, representing a Zinc-cadmium ratio of 0.4, the flow point of the alloy increases to 1135 F. Accordingly, the alloys of lowest flow point, which contain silver and copper in a total amount of 55% and in a ratio of about 3.4, are those, in which the zinc-cadmium ratio lies between 0.5 and 1.

It will be seen, accordingly, that in a quaternary alloy composed of silver, copper, zinc and cadmium, a low flow point of about 1125 F. can be achieved by using 42.5-43% silver and 12- 12.5% copper, the silver and copper totalling 55% of the alloy, and by making up the balance of the alloy composition with 15 to 22.5% zinc and 22.5 to 30% cadmium while maintaining a zinc-cadmium ratio within the range of 0.5 and 1. The resulting alloy composition is characterized by a lower flow point and a lower silver content than the alloy of my above-identified prior patent and is therefore superior to said prior alloy composition in utility and cost.

This application is a division of my co-pending application Serial No. 610,752, filed August 14, 1945, now abandoned.

I claim:

1. A quaternary alloy of silver, copper, zinc and cadmium having a flow point of about 1125 F. and consisting of 42.5-43% silver, 12-12.5% copper, 15 to 22.5% zinc and 22.5 to 30% cadmium, the silver and copper totalling 55%, and the zinc and cadmium totalling and being present in a ratio within the range of 0.5/1 and 1/1.

2. A quaternary alloy of silver, copper, zinc and cadmium having a flow point of about 1125 F. and consisting of 43% silver, 12% copper, 22.5% zinc and 22.5% cadmium.

ROBERT H. LEACH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 20,638 Leach Jan. 25, 1938 1,899,701 Leach Feb. 28, 1933 2,019,984 Leach Nov. 5, 1935 2,235,634 Hensel et a1 Mar. 18, 1941 2,310,231 Goldsmith Feb. 9, 1943 2,362,893 Durst Nov. 14, 1944 2,383,976 Leach Jan. 25, 1945 FOREIGN PATENTS Number Country Date 558,873 Great Britain Jan. 25, 1944 

